The present invention relates to a header assembly for mounting to a circuit substrate and for receiving a complementary electrical connector. In particular, the present invention is for a high density header assembly for use in, for example, a motherboard in a backplane/back panel application.
In a typical electrical interconnection system, a first removably insertable circuit board includes a complementary electrical connector that is to be mated with a header assembly or header which is mounted to a second circuit board. As should be understood, when the first circuit board is coupled to the second circuit board by way of the electrical connector and header and when the first circuit board is in operation, a number of signals enter or leave the first circuit board through conductive paths defined by the electrical connector on the first circuit board and the header on the second circuit board. In many instances, the second circuit board has other circuit boards coupled thereto by other respective headers and complementary electrical connectors, and the aforementioned signals can originate from or be destined for such other circuit boards. Of course, the aforementioned signals can also originate from or be destined for other locations remote from the second circuit board by way of appropriate interconnections.
If it is desirable to suppress signal noise and/or cross-talk, it is known that a signal may be transmitted over a pair of differential (positive and negative) signal lines that travel together in close proximity. Typically, in such pair of differential lines, the signal itself (+V) is transmitted on the positive line, and the negation of the signal (xe2x88x92V) is transmitted on the negative line. Since both lines travel together in close proximity, any noise encountered by the lines should appear in a generally identical form on both lines. Accordingly, the subtraction (by appropriate circuitry or other means) of the negative line (xe2x88x92V+noise) from the positive line (+V+noise) should cancel out such noise ((+V+noise)xe2x88x92(xe2x88x92V+noise)=2V), thus leaving the original signal, perhaps with a different amplitude.
Oftentimes, in a high frequency environment, most every signal passing to and from a circuit board travels as a pair of differential signals on a pair of differential signal lines. Accordingly, the electrical connector on the circuit board and the header on the backplane must accommodate all such pairs of differential signal lines. Moreover, with increased contact density on a circuit board, there has been a corresponding increase in signal lines associated with such circuit board. As a result, the number of individual lines running through the electrical connector of the circuit board and the associated header can be quite large. At the same time, since it is desirable to increase the number of circuit boards that can be coupled to the backplane, the xe2x80x98real estatexe2x80x99 on the backplane used by the header must be kept small. Therefore, the xe2x80x98densityxe2x80x99 of individual signals that pass through the electrical connector and header must be increased.
With such increased density, however, the issue of susceptibility to noise and/or cross-talk again arises, even in electrical connectors and headers that transmit pairs of differential signals. To combat such density-based noise, the header in particular has been modified to include ground shielding which substantially electromagnetically isolates within the header each pair of differential signal lines from every other pair of differential signal lines.
Accordingly, a need exists for a header that can have multiple differential signal pairs in relatively high density, and that has ground shielding for the signal pins, where the header is practical and relatively easily manufactured.
An example of such a header is disclosed in U.S. patent application Ser. No. 09/302,027, as was disclosed and incorporated by reference above. Such a header has proven to be remarkably capable of reducing noise and/or cross-talk. However, the particular design of the header disclosed in such application does not have an especially high tolerance for margins of error in dimensions of parts thereof. For example, the features responsible for maintaining interference fits of such parts are not flexible, and accordingly, fail to in fact effectuate such interference fits if not dimensionally precise.
That is, most header parts re inserted into apertures in a header base and held therein by interference fits assisted by various interfacing bumps on the parts. In particular, if an aperture in the header base is slightly too wide, or if an interfacing bump on a part that is to be inserted into the aperture is slightly too short, such bump will not contact the inner wall of such aperture once the part is inserted, and will not help to hold the part within the aperture by way of an interference fit. As a result, intermittent electrical connection could occur. Also, the part can fall out of the base. Conversely, if an aperture in the header base is slightly too narrow, or if an interfacing bump on a part that is to be inserted into the aperture is slightly too tall, such bump will exert excessive force on the inner wall of such aperture once the part is inserted, and may in fact result in excessive strain on the base which can lead to immediate or eventual structural failure. As a result, the header is destroyed.
Accordingly, and moreover, a need exists for such a header wherein the header has a relatively high tolerance for margins of error in dimensions of parts thereof.
The present invention satisfies the aforementioned need by providing an electrical connector that has a base defining a plurality of aperture spaces therein. A plurality of contacts are received and secured within the aperture spaces, and include signal contacts and ground contacts. In addition, a plurality of ground shields are received and secured within the aperture spaces.
The ground shields are positioned to shield selected ones of the signal contacts from noise and/or cross-talk generated by other signal contacts within the base. Each ground shield has an electrical contact site at which the ground shield is in physical and electrical contact with a ground contact. The electrical contact site is flexible.